Lanthanum-promoted copper-based hydrotalcites derived mixed oxides for NO_x adsorption, soot combustion and simultaneous NO_x-soot removal

Graphical abstract: - Highlights: • The addition of La in Cu-based oxides increased the types of active oxygen. • NO_x adsorption, soot oxidation and simultaneous NO_x-soot removal were enhanced. • The possible catalytic mechanism was studied via in situ FTIR analysis. • Soot oxidation was promoted by the NO₂ intermediate. - Abstract: La-promoted Cu-based hydrotalcites derived mixed oxides were prepared and their catalytic activities for NO_x adsorption, soot oxidation, and simultaneous NO_x-soot removal were investigated. The catalysts were characterized by XRD, DTG, BET, FTIR, H2-TPR, TPD and TPO techniques. The oxides catalysts exhibited mesoporous properties with specific surface area of 45–160 m²/g. The incorporation of La and Cu decreased the amount of basic sites due to the large decrease in surface areas. Under O₂ atmosphere, La incorporation is dominant for soot oxidation activity, while Cu favors high selectivity to CO₂ formation. A synergetic effect between La and Cu for catalyzed soot oxidation lies in the improved redox property and suitable basicity. The presence of NO in O₂ significantly promoted soot oxidation on the catalysts with the ignition temperature decreased to about 300 °C. In O₂/NO atmosphere, NO₂ acts as an intermediate which oxidizes soot to CO₂ at a lower temperature with itself reduced to NO or N₂, contributing to the high catalytic performance in simultaneous removal of NO_x and soot